Implement info command for SysV IPC mqs

The `list` command was refactored a little bit as well and the man
page and readme were updated.

src/main.rs

@@ -25,6 +25,7 @@ enum PosixCommand {
 #[derive(Clap, Debug)]
 enum SysvCommand {
     Create(sysv::Create),
+    Info(sysv::Info),
     List(sysv::List),
     Unlink(sysv::Unlink),
 }
@@ -70,6 +71,7 @@ fn main() -> Result<()> {
         },
         Backend::Sysv(s) => match s {
             SysvCommand::Create(c) => c.run()?,
+            SysvCommand::Info(i) => i.run()?,
             SysvCommand::List(l) => l.run()?,
             SysvCommand::Unlink(u) => u.run()?,
         },

src/sysv.rs

@@ -1,7 +1,9 @@
 mod create;
+mod info;
 mod list;
 mod unlink;
 
 pub use create::Create;
+pub use info::Info;
 pub use list::List;
 pub use unlink::Unlink;

src/sysv/info.rs

@@ -0,0 +1,53 @@
+use anyhow::Result;
+use clap::Clap;
+use std::{
+    fs::File,
+    io::{BufRead, BufReader},
+};
+
+/// Print information about an existing message queue
+#[derive(Clap, Debug)]
+pub struct Info {
+    /// Id of the queue
+    #[clap(short, long, required_unless_present_any = &["key"], conflicts_with = "key")]
+    id: Option<i32>,
+    /// Key of the queue
+    #[clap(short, long, required_unless_present_any = &["id"], conflicts_with = "id")]
+    key: Option<i32>,
+}
+
+fn print_line(line: &str) {
+    for field in line.split_whitespace().collect::<Vec<&str>>() {
+        print!("{0: <10}", field);
+    }
+
+    println!();
+}
+
+impl Info {
+    pub fn run(&self) -> Result<()> {
+        let mut lines = BufReader::new(File::open("/proc/sysvipc/msg")?).lines();
+
+        print_line(&lines.nth(0).unwrap_or(Ok(String::new()))?);
+
+        for line in lines {
+            let line = line?;
+
+            if let Some(id) = self.id {
+                if id == line.split_whitespace().collect::<Vec<&str>>()[1].parse::<i32>()? {
+                    print_line(&line);
+
+                    break;
+                }
+            } else if let Some(key) = self.key {
+                if key == line.split_whitespace().collect::<Vec<&str>>()[0].parse::<i32>()? {
+                    print_line(&line);
+
+                    break;
+                }
+            }
+        }
+
+        Ok(())
+    }
+}

src/sysv/list.rs

@@ -11,9 +11,7 @@ pub struct List {}
 
 impl List {
     pub fn run(&self) -> Result<()> {
-        let file = BufReader::new(File::open("/proc/sysvipc/msg")?);
-
-        for line in file.lines() {
+        for line in BufReader::new(File::open("/proc/sysvipc/msg")?).lines() {
             for field in line?.split_whitespace().collect::<Vec<&str>>() {
                 print!("{0: <10}", field);
             }

src/sysv/unlink.rs

@@ -7,14 +7,14 @@ use log::info;
 pub struct Unlink {
     /// Id of the queue
     #[clap(
-        long,
         short,
+        long,
         required_unless_present_any = &["key"],
         conflicts_with = "key"
     )]
     id: Option<i32>,
     /// Key of the queue
-    #[clap(long, short, required_unless_present_any = &["id"], conflicts_with = "id")]
+    #[clap(short, long, required_unless_present_any = &["id"], conflicts_with = "id")]
     key: Option<i32>,
 }